The present invention relates to warning devices, and in particular to an improved fire detector having means for perceptibly indicating its various states and conditions of operation.
To provide maximum fire protection, it is desirable to monitor the operation of a fire detection device to ensure that the device is adequately powered and is otherwise operating properly. To this end, it is also desirable to provide sensibly discernible indications of the various states and conditions of operation of the detector so that, for example, a user thereof may readily be apprised of the need to take correction action should its operation be amiss.
Where the fire detector is battery powered, a decrease in the energy level of the battery to below a level sufficient to properly operate the detector not only is undesirable, but is intolerable, since such may result in failure of the unit to generate an alarm upon the occurrence of combustion. Merely instructing a user of the device to replace the battery after a predetermined period of time is unsatisfactory, since it is likely that the instructions will either be forgotten or unheeded, ultimately resulting in failure of the detector. Further, due to variations between individual batteries which cause the lengths of their useful lives to vary considerably one from the other, it is possible that a battery may fail before the end of its expected useful life. Consequently, battery powered devices such as fire detectors should be provided with some means for warning users of impending battery failure.
Fair and smoke detectors commonly employ a sensor, such as one or more photocells or ionization chambers, for detecting products of combustion. A disadvantage encountered with such sensors is that certain conditions which occur within the sensor, such as an accumulation of films of dirt and dust, etc., may result in a decrease in the sensitivity of the detector to products of combustion. Should this happen, it is possible that combustion may reach an advanced stage before being detected. Therefore, the detector should also be provided with some means for warning a user of a decrease in the sensitivity thereof and of the need to service the unit to bring the sensitivity back to a nominal level.
In certain uses of fire detectors, such as in multiunit apartment buildings, the detectors often are connected in a system, so that all of the devices generate an alarm upon the detection of products of combustion by any one of the devices. In this manner, should a fire occur anywhere throughout the building, the occupants of all of the units are warned. Since the source of the combustion is not always readily visible or easily discernible, with such systems it is both desirable and advantageous that each individual detector be provided with some means for indicating whether it is generating the alarm in response to detection of combustion by another detector, or if it has itself initiated the alarm.